Getting Hotter

[Mark Woodland]

Greetings,
I just replaced the heater control valve on my '86 5KTQW with an Autozone
manual valve, 3/4", to close the damn thing for good, in the summer.
My theory, that which is mine, is as follows:
Even if you have a good vacuum actuated valve, the vacuum (most likely)
comes off when the car is off.
Therefore, its cool when you start out, but stop and park it for a few../.
to pick up something/run an errand, and the valve opens up, allowing the
dreaded "thermal siphon" effect to fill the heater core with hot antifreeze.
Start back up, the valve closes and you have to fire the A/C to cool the
heater core down.
If the A/C is non-operable... (like mine), the air coming through the system
is MUCH hotter now, and will take 1/2 hour +, driving at high rates of
speed, to get the temp down to where its only 5 to 10 degrees above ambient.
Good mind numbing stuff.
If that shutoff valve works, I'll do it to Max, too, but for now, the A/C
works in Max, and the additional thermal load is negligable.
Whoever asked about the test for the valve... take the thing out, hold it in
your hand, manually close the "Gate valve", and blow through it.
If its anything like mine was, having the valve closed slowed it down some,
but the air (or hot antifreeze) blew right on by...
Before pulling it, I also determined that there was no vacuum being applied
to the valve, when the system was set to "Lo Temp".
Check it out, we may be onto something here...
If anyone wants to know, the Autozone part number for the manual valve is
84707.. under $10.00. What a deal.
It ain't A/C, but it beats Hell out of having the heat on in weather like
this.
Mark
Stay cool

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